Plate positioning arrangement for plate finishing machine



0st. 4, 1960 c. SLCRAFTS ETAL 2,954,598

PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE 6 Sheets-Sheet1 Filed Feb. 20, 1957 INVENTORS CURTIS S. CRAFTS Awvs.

CORSON WALTER CHASE GLENSQ. Knueaan Oct, 4, 1960 c. s. CRAFTS ETAL PLATEPOSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE Filed Feb. 20, 19576 Sheets-Sheet 2 s y m R R T 0 SH E T T H m% A Nmmu r cu K V .A v SWTAKQNN o Sm um. c

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Oct. 4, 1960 c. s. CRAFTS ET-AL PLATE POSITIONING ARRANGEMENT FOR PLATEFINISHING MACHINE Filed Feb. 20, 1957 6 Sheets-Sheet 4 INV ENTOR CURTIS5. CRAFTS CORSON WALTER CHASE GL/ENN N. KRUEGER Oct. 4, 1960 c. s.CRAFTS ETAL PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINEFiled Feb. 20, 1957 6 Sheets-Sheet 5 IFIIIIIIII! INVENTOR CURTIS S.CRAFTS Corason WALTER CHASE Es KZZEIGEW Ill 2,954,598 PLATE POSITIONINGARRANGEMENT FOR PLATE FINISHING MACHINE Filed Feb. 20. 1957 Oct. 4, 1960c. s. CRAFTS ETI'AL 6 Sheets-Sheet 6 R. Nb

ll N HH INN "will! 11111111 1 I I. \\\\\WN M M$ Mb INVENTORS Cunns5.CRAFTS Coasow WALTER CHASE GLENN N. KRUEGER 1332 Q ,I

II==F PLATE POSITIONING ARRANGEMENT FOR PLATE FINISHING MACHINE CurtisS. Crafts and Corson Walter Chase, Oak Park, and Glenn N. Krueger, NorthRiverside, Ill., assignors to Miehle-Goss-Dexter, Incorporated,Wilmington, Del., a corporation of Delaware Filed Feb. 20, 1957, Ser.No. 641,319

8 Claims. (CI. 29-21) This invention relates to machines for milling thetension lockup pockets in stereotype printing plates and moreparticularly to plate registering methods and apparatus for use withsuch machines to properly position plates for the milling operation.

Different arrangements are known to hold stereotype printing plates onthe cylinders of a printing press. One such arrangement utilizes tensionlockup holding mechanism which include hooks or fingers which engage theplates and apply circumferential tension to draw them securingly againstthe press cylinders. For receiving the hooks or fingers of the plateholding mechanisms, recesses, called tension lockup pockets, are milledin the underside of the curved printing plates adjacent their straightedges. It is customary to mill such recesses or pockets after theprinting plates have otherwise been completely prepared for printing,including the step of shaving the undersides of such plates to afinished dimension conforming to the outer surface of a printingcylinder, in order to obtain accuracy in locating the tension lockuppockets.

In the case of plates intended for ordinary black and white reproductionprecise adjustment of position may be accomplished with the usualside-lay and circumferential adjustments provided on the cylinders.However, in the case of three color printing, precise register of thecolors requires that the plates be slightly distorted longitudinally andcircumferentially in addition to being precisely positioned bothcircumferentially and axially.

Milling machines particularly adapted to prepare stereotype printingplates by cutting pockets' on the underside of the plate have becomewell known. An example of an improved plate milling machine of this typemay be seen by reference to applicants co-pending application, SerialNo. 641,176, filed February 19, 1957. Since the tension lockuppocketsformed by machines of this type must be accurately located withrespect to the printing image on the plates, particularly when theplates are intended for color printing, the method and apparatus used toregister a stereotype plateon the pocket milling machine is ofsubstantial importance.

It is thus an object of the present invention to provide improved plateregistering apparatus and procedure for a pocket milling machine whichenables a set of color printing plates to be milled so that when mountedin the press they automatically occupy positions of precise registerwith respect to one another. It is an object to provide a novelprocedure for accomplishing the above which is simpler and more rapid,hence more economical, than conventional procedures. It is a relatedobject to provide a plate positioning procedure and apparatus for apocket milling machine which dispenses with the reference marks, such aspointers, cross hairs, etc., which characterize conventional devices andwhich instead provides for positioning each of a succession of colorplates using any selected critical area of such plates as theregistering criterion. More specifically it is an object to provide anapparatus which permits visual access to all portions of the copy sothat any portion is available for registering purposes when using theimproved procedure.

It is another object of the invention, in one of its aspects to providean improved image transferring arrangement to permit preciseregistration of a reference image with the copy on successive colorplates comprising a set which may be readily swung out of the way with ahinging action for substitution of plates but which upon being replacedoccupies exactly tthe same position without dependence on hingemechanism.

It is a further object to provide a milling machine which is ideallysuited for registered milling of a set of colored plates but which maybe used with equal facility in the preparation of plates for black andwhite printing.

With more particularity, it is an object to provide a novel support forprinting plates in a pocket milling machine of the above type whichpermits the plates to be smoothly slid onto, and eventually slidthrough, the machine without lifting or other manual effort and whichincludes novel positioning stops which retract so as not to hinder thefree sliding movement of the plate. It is a related object of theinvention to provide a novel distorting stop construction which enablesthe relatively high distorting pressures to be developed but which isnevertheless easily adjusted with light manual pressure and inherentlystrong, requiring little or no maintenance even in the face of constanthard usage.

It is a further object to provide a registering apparatus of the typereferred to above that is rugged and sturdy so as to be suitable forlong, heavy duty operation without losing its accuracy.

Other objects and advantages of the invention will become apparent uponreading the attached detailed description and upon reference to thedrawings in which:

Figure l is a perspective view of a tension lockup pocket millingmachine embodying the present invention.

Fig. 2 is a transverse section of the milling machine shown in Fig. 1showing the milling cutters in operation.

Fig. 3 is a fragmentary end view, partially in section, of the machineshown in Fig. 1.

Fig. 4 is a fragmentary end view, partially in section, of the oppositeend of the machine shown in Fig. 1.

Fig. 5 is a fragmentary, longitudinal sectional view of a portion of themachine shown in Fig. 1.

Fig. 6 is a perspective view showing a registering device in use,constructed in accordance with the present invention.

Fig. 7 is a plan view showing the registering device in position on themilling machine of Fig. l and with parts of the machine omitted.

Figs. 8 and 9 are fragmentary transverse sectional views taken alonglines 8-8 and 9-9, respectively, of Fig. 7.

Fig. 10 is a fragmentary plan view of the machine shown in Fig. 1 withthe clamps omitted.

Fig. 11 is a fragmentary elevational view of the machine shown in Fig.1.

Fig. 12 is a plan view of a stop device as utilized in the machine ofFig. 1, constructedaccording to the present invention.

. Fig. 13 is an elevation view of the stop structure shown in Fig. 12. V

Fig. 14 is an end view of the stop structure shown in Fig. 12.

Fig. 15 is a fragmentary view similar to Fig. 13 showing the stop in aretracted position.

While the invention will be described in connection with a preferredembodiment and procedure, it will be understood that I do not intend tolimit the invention to that embodiment and procedure, but on thecontrary, intend to cover all alterations, modifications and equiva-Patented Oct. 4, H260.

lents as may be included within the spirit and scope of the invention asdefined by the appended claims.

General description of the milling machine Turning first to Fig. 1,there is shown a tension lockup pocket milling machine which is designedto accept semi-cylindrical curved stereo-type printing plates P and cutrows of tension lockup pockets TP into the inner cylindrical surface ofthe printing plate (see Fig. 2). The machine 10 is of a type more fullyand completely described in applicants related application Serial No.641,176, filed February 19, 1957, to which reference may be had foradditional details of the machine construction and operation.

Briefly, the milling machine 10 comprises a base frame 11 on which issupported a semi-cylindrical saddle 12 that is proportioned to uniformlyengage and support the finished, inner, cylindrical surface of astereotype printing plate P. The saddle 12 is hollow and a pair ofmilling cutters 13 and 14 (see Fig. 2) are mounted for longitudinalreciprocation within the saddle.

Supporting and carrying the milling cutters 13 and 14 is a travelingcarriage 15, which reciprocates within the base frame 11 and below thesaddle 12 along the longitudinally extending ways 16 and 17. As thecarriage carries the milling cutters 13, 14 beneath the plate P, thecutters are urged outwardly through openings 18 and 19 formed in thesaddle 12 so as to selectively engage the inner surface of a printingplate P and cut the desired tension lockup pockets TP.

In order to hold the stereotype printing plate P in position during themilling operation, the machine 10 is provided with a clamping structurewhich is effective to press downwardly and hold the plate P on thesaddle 12. The clamping structure comprises two arcuate clamp units 21,22 which slide in spaced relation to the saddle 12 along parallellongitudinal rods 23 and 24. The clamp units 21, 22 are of a type morefully described in applicants related application Serial No. 641,056,filed Pebruary 19, 1957, and reference may be had to this applicationfor details of construction and operation. It will be sufiicient forpresent purposes to recognize that the clamp units 21, 22 may be slidalong their supporting rods 23, 24 to a position overlying a printingplate P on the saddle 12 where the clamp units 21, 22 can be activatedso as to press the plate P uniformly and firmly against the saddle 12,thus fixing the printing plate with respect to the cutting pathsfollowed by the milling cutters 13, 14.

To assure that printing plates being cast and finished to a particularset of dimensions are firmly supported on the saddle 12 withoutlooseness, the saddle 12 is pro- 'vided with edge supporting means whichmay be properly positioned to exactly support a particular set ofstereotype printing plates. In the illustrated embodiment the supportingmeans takes the form of a pair of eccentric cams 26, 27 (see Fig. 11)mounted on each side of the saddle 12. The cams 26, 27 of each pair maybe properly adjusted and fixed in position, by loosening and thentightening a central cam mounting screw, so that the peripheries of thecams engage and support the straight longitudinal edges of a printingplate P when the inner curved surface of the plate rests in smoothengagement with the saddle 12.

Plate supporting apparatus Since the cutting path followed by themilling cutters '13, 14 is automatically controlled and thus remains thesame for each successive milling operation, it is apparent that theposition of the printing plate P itself must be altered to properlyorient the cutting path and the plate. Therefore, in order .to preciselyposition the tension lock up pockets TP with respect to the printingimage on the outer surface of the printing plate means are provided toboth rotate and axially shift the saddle 12 so that the plate P may becarried into proper alinement.

Turning to the illustrative rotatable and shiftable mounting for thesaddle 12, shown in Figs. 3, 4 and 5, it can be seen that the saddle. 12is provided with axially alined trunnions 31, 32 supported for bothrotating and sliding movements within bearings 33, 34, respectively,which are suitably fixed within the machine frame 11. In order to rotatethe saddle 12, a shaft extension 35, extending axially from the trunnion31, is slidably keyed to a rocking arm 36. Rocking of the arm 36 isaccomplished by rotating an adjusting screw 37 that is fixed againstaxial movement in the frame 11 and threaded into a nut 38 carriedbetween the bifurcated lower end 39 of the rocking arm 36. Forconvenience in rotating the adjusting screw 37, a handle 40 is providedat its outer end. It will be apparent that by rotating the handle 40,the screw 37 is revolved within the nut 38 thereby forcing the nutlaterally and rotating the lever 36 which in turn rotates the saddle 12.

In order to shift the saddle 12 axially, the trunnion 32 is providedwith an axially alined shaft extension 43 to which is pinned a sleeve 44having an external helical thread. Threaded onto the sleeve 44 is a nut45 held axially captive within a gear housing 46 formed integrally withthe machine frame 11. Since the nut 45 is restrained against axialmovement, it is apparent that rotation of the nut will cause axialmovement of the sleeve 44 to which it is threaded, and thus will axiallyshift the entire saddle 12. To rotate the nut 45, it is provided with aworm gear on its periphery which engages an adjusting worm 4-7 on ashaft 43. \For convenience in rotating the adjusting shaft 48, a handle50 is fixed to the outer end of the shaft. It will be apparent thatrotating the adjusting shaft 48 causes the worm 47 to rotate the nut 45and thus shift the saddle 12 axially.

It can thus be seen that by the manipulation of handles 40 and 50, thesaddle 12 may be axially and peripherally shifted so as to carry aprintingplate P into a desired position with relation to the cuttingpaths of the milling cutters 13, 14. It has been found in practice thatonly small amounts of axial and rotational movements are required toaccomplish the desired results, a total of A usually being sufficient.However, it will be understood that this structure cannot be effectiveunless utilized in conjunction with some means for indicating to anoperator the proper position of the saddle that will precisely positionthe plate with respect to the milling cutters. Furthermore, thoseskilled in the art will appreciate that stereotype printing plates ofencarry copy, i.e., a printing image, that is slightly distorted due tounavoidable factors in the plate casting process. This means that theprinting image can not be completely positioned by merely shifting theprinting plate axially and peripherally by positioning the saddle 12.

Positioning and skewing stop structure clamping the plate adjacent eachof its straight edges, with.

provision for moving the stops independently to distort the platelongitudinally and circumferentially so that it may be clamped indistorted position during the milling of the pockets. The stops areresiliently mounted and shaped-to permit a plate to slide easily overthem in one direction by carnming the stops to a retracted position. Inaddition, the saddle 12 is provided with adjustable distorting stopsconstructed to permit their easy retraction beneath the saddle surfaceso that a plate P may pass thereover, and which together with thepositioning stops, are effective for distorting the plate Plongitudinally and circumferentially for precise registration. In thepresent embodiment two positioning stops 61 and 62 and two distortingstops 63 and 64 are provided (see Fig. 10). The stops 62, 6.4

are mounted in extensions in the opening 18 formed i through the saddle12, while the stops 61, 63 are mounted in the similar but oppositeopening 19. The construction of each of the stops 6164 is substantiallyidentical, with the two distorting stops having an adidtional featureincident to their function, and therefore it will be convenient todescribe in detail only the distorting stop 63 for illustrativepurposes. It will be understood that the distorting stop 64 is identicalto the stop 63, and that the positioning stops 61, 62 are also identicalexcept for the omission of certain parts, as will be made clear below.

Referring to Figs. 12-15, the distorting stop 63 comprises a finger 65having an inversely inclined abutment face 66 and a sloping uppersurface 67. The finger 65 is journaled by means of a pin 68 within thebifurcated end of a mounting block 69. To urge the finger 65 into itsupraised, operative poistion, a resilient fiat spring 70 is fastened tothe bottom of the mounting block 69 and extends forwardly to bearagainst a lower lip 71 on the finger '65. When the finger 65 is swungdownwardly so that its surface 67 is below and approximately parallel tothe surface of the saddle 12, the lower lip 71 flexes the spring 70 (seeFig. 15) so that there is imposed a resilient force urging the finger 65into its upraised, operational position.

To positively limit the upward swinging movement of the finger 65, it isprovided with a positioning pin 72 that extends laterally from each sideof the finger and engages forwardly extending lugs 73, 74 formed at thebifurcated ends of the mounting block 69. It will be apparent that theengagement of the pin 72 with the lugs 73, 74 provides a positive limitto the upward swinging movement of the finger 65.

In order to permit movement of the stop 63 axially of the saddle 12, themounting block 69 is slidably supported in an opening formed in thesaddle and a positioning screw is provided to move the mounting blockalong the opening. In the illustrated embodiment, the block 69 isprovided with integrally formed, laterally extending ledges or tongues80, 81 which slidingly fit within grooves 82, 83, respectively, formedin the saddle 12. A rotatable adjusting screw 84 is held captive at therear end of the mounting block 69 by means of a set screw 85 threadedinto the block which engages the side walls of a groove 86 formed at theend of the adjusting screw 84. It will be apparent that thisconstruction permits the adjusting screw 84 to be rotated relative tothe block 69, but that the block will be moved axially with theadjusting screw. To cause the adjusting screw 84 to move axially andthereby position the mounting block 69, the screw is threaded into a nutportion 87 formed integrally with the under surface of the saddle 12 andextends outwardly through the end of the saddle to support a handle 88.It will be understood that by manually rotating the handle 88, theadjusting screw 84 is threadably advanced or retracted through the nutportion 87 and will be effective to slide the mounting block 69 alongthe grooves 82, 83 to any desired position. i

The stop structure thus far described is common to all of the fourstops, including the positioning stops 61, 62. In the case of thepositioning stops 61, 62, it will be apparent that printing platessliding along the saddle 12 from right to left in Fig. 1, will engagethe upper sloping surfaces of the pivoted fingers forming parts of thestops 61, 62 and cam them downwardly into retracted position beneath thesurface of saddle 12. Thus, the plates need not be lifted onto themilling machine but may he slid onto the saddle 12 from an adjoiningplate finishing machine. As soon as a plate has passed beyond thepivoted fingers of stops 61, 62, the fingers will snap to their upraisedpositions with their inversely inclined forward faces providing aconvenient abutment against which the plate may be properly positionedon the saddle 12.

The stops 61, 62 are also provided with adjusting handles 90, 91respectively,which are equivalent in construction and function to thehandle 88 described in connection with distorting stop 63. It will thusbe appreciated that by rotating the handles 90, 91, the positioningstops 61,62 may be moved axially of the saddle 12. The distorting stop64 is identical to the stop 63 and is similarly provided with anadjusting handle 89 permitting axial movement of the stop 64. The stops6164 may therefore be easily adjusted to accommodate plates rangingwidely in size, as from the smaller plate shown in dot-dash outline inFigs. 10, 11 to the longer plate outlined in dashed lines in thosefigures.

It can thus be seen that by moving companion distorting and positionstops together in either direction, i.e., stops 64 and 62 or 63 and 61,non-alined forces are exerted causing a twisting force to be imposed ona plate positioned between the stops which will be effective to slightlydistort the printing plate bot-h longitudinally and circumferentially.The inversely inclined abutment faces of the positioning and distortingstops, such as face 66 of the stop 63, will exert a downward componentof force when the stop is tightened against a printing plate P so thatthe plate is firmly retained on the saddle 12.

Returning to the construction of the distorting stops 63, 64, it is afeature of the invention that the stops may be quickly retracted beneaththe surface of the saddle 12 so as to permit a printing plate P to heslid over them and off of the saddle. In the illustrated embodiment thestop 63, which is identical to the stop 64, is provided with anadjustably positionable tilting rod which is threadably fixed to a clampblock 96. The rod 95 extends through a bore 97 formed in the mountingblock 69 to bear against the rear surface of the finger 65, sufiicientclearance being provided in the bore so that the rod and clamp block can-move freely. The block 96 includes laterally extending ledges 98 and 99(see Fig. 12) which are adapted to ride within the grooves 82, 83. Inorder to clamp the block 96 into position, two screws 101, 102 arepassed through the block 96 and threaded into a strap block 103positioned beneath the clamp block 96 and in engagement with theunderside of the saddle 12. It can be seen that by tightening the screws101,102, the strap block is drawn tightly against the underside of thesaddle 132, thus clamping the block 96 in place and fixing the tiltingrod 95 with respect to the mounting block 69.

In operation, the tilting rod 95 contacts the finger 65 above the axisof the finger pivot pin 68 when the mounting block 69 is drawnrearwardly along the grooves 82, 83 so that further rearward motion ofthe block 69 with respect to the tilting rod 95 causes the finger 65 topivot forwardly, i.e., clockwise in Figs. 13 and 15, to its flushposition below the surface of the saddle 12 (see Fig. 15). It will beappreciated then, that the handles 88, 89 not only permit the distortingstops 63, 64 to be advanced in order to distort a printing plate P, butalso cause the stops 63, 64 to be retracted into their out-of-the-wayposition. The tilting rods for the stops such as rod 95 for the stop 63,may be adjustably positioned so that only a slight withdrawal of themounting block causes the stop finger to retract, and thus it requiresonly a quick spin of the handles 88, 89 to clear the surface of thesaddle 12 and allow a printing plate P to be slid along the saddle, overthe distorting stops 63, 64, and off the milling machine 10.

In order to prevent the accidental distorting of a printing plate Pbeyond the elastic limit of the plate material, each of the adjustinghandles 88, 89, 98, 91 is provided with a travel limiting shim, of whichonly the shim 92 for the handle 88 is identified in the drawings (seeFigs. 12, 13). The shim 92 is selected to be of such a thickness thatthe handle 88 can be advanced only approximately 1 of an inch before theshim 92 comes in abutting contact with the end of the saddle 12. This,of course, limits the forward distorting movement of the stop 63 to thatsame distance,-and therefore prevents accidental permanent distortion ordamage to a plate P being distorted or twisted into proper registry onthe saddle 12.

7 Transparent sheet structure The present invention is also concernedwith the provision of a readily detachable and simply used transparentsheet structure for accurately establishing a reference image that isprecisely alined with the cutting path of the milling cutters 13, 14 andthus permits precise orientation of the entire printing image on aseries of color printing plates. The registering apparatus comprises aflexible transparent sheet 110 (see Figs. 6, 7, 8 and 9) which isreleasably pivoted at one side of the saddle 12 and is provided with aweighted bar 111 at its opposite edge that is effective to smoothlytension the transparent sheet 110 over the outer surface of a printingplate P supported on the saddle 12.

In order to releasably pivot the sheet 110, the latter is provided witha strap 112 along one edge from which hook members 113 depend at eachend. The hook members 113 may be snapped about pivot pins 114, each ofwhich cooperate with a retaining spring 115 (see Fig. 8) to cause themember 113 to be received with a detent action. The pivot pins 114-extend inwardly from two alining blocks 116, 117, which in turn arefastened to an upstanding, angle bracket 118 that is mounted on the baseframe 11. When the hook members 113 are snapped over the pivot pins114-, they are held on the pins by the resilience of the springs 115,and each of the hook members 113 is then disposed in close fitting,sliding engagement between the alining blocks 116, 117.

To ensure that the opposite edge of the transparent sheet 110 islikewise exactly positioned, the weighted bar 111 is closely andslidably fitted between two alining blocks 121, 122, which are securedto an upstanding angle bracket 123 fastened to the machine frame 11. Topermit the convenient handling of the transparent sheet 116,

the strap 112 is provided with a handle 12 1, and the weighted bar 111is provided with a similar handle 125.

In operation, the hook members 113 are snapped over the pivot pins 114and the transparent sheet 110 laid over a printing plate P carried onthe saddle 12. The weighted bar 111 will then rest between the aliningblocks 121, 122. It can be readily seen that the alining blocks 121,122, cooperating with the weighted bar 111, and the alining blocks 116,117, which cooperate with the hook members 113, serve to keep thetransparent sheet 110 precisely positioned with respect to the frame ofthe milling machine 10, although the printing plate P may be shifted orrocked beneath the transparent sheet. When the transparent sheet is nolonger in use, it may be quickly lifted from the saddie 12, utilizingthe handles 124, 125, and unsnapped from the pivot pins 114 so that itmay be placed in an out of the way position where there is no likelihoodof accidental damage.

Operating procedure Following the preferred procedure, the key or blackplate of a given color series is first slid onto the saddle 12 andagainst the positioning stops 61, 62. At this time it is desirable tohave turned the hand wheels 40, t and to have adjusted the positioningscrew handles 90, 91 so that the saddle 12 and the positioning stops 61,62 are in intermediate positions, free to be adjusted in either of theirdirections of possible movement. To conven iently indicate theintermediate positions of the saddle 12 and the positioning stops 61,62, suitable indicia marks, e.g., 61a, 62a, can be etched or otherwiseplaced on adjacent relatively movable parts in the conventional mannerwell known to those skilled in the art.

With the parts in their intermediate positions, and the black or keyplate supported on the saddle 12, the transparent sheet 1111 is pivotedto the side of the saddle in the manner described above and an image istransferred from the key or black plate to the underside of thetransparent sheet 1111 by utilizing proofing ink on the plate androlling the sheet over the plate. The plate is then clamped firmly onthe saddle 12 by clamp units 21, 22.

and the tension lockup pockets are milled in the underside of the plate.

Other plates which are intended to print the additional desired colorsto make up the final color image, are then positioned one by one on thesaddle 12 adjacent the positioning stops 61, 62. The transparent sheetis laid over each subsequent plate and is precisely re-positioned by theoperation of the alinement blocks 116, 117, 121, 122, all as previouslydescribed. Since the key of reference image is printed on the undersideof the transparent sheet 110, the saddle 12 can be manipulated by thehand wheels 411, 50 to bring a critical portion of the printing image onthe plate precisely beneath the corresponding portion of the referenceimage. As is readily apparent in Fig. 6, the printing and referenceimages are clearly visible in their entirety, and thus exact orientationof the most critical portion of the color image can be easily sought andobtained.

Following the peripheral and axial shifting of the saddle 12 to bringthe critical portion of the printing image in coincidence with theoverlying reference image on the transparent sheet 110, the adjustingscrews 81} to 91 can be manipulated, if required, to apply non-alinedforces and slightly distort the printing plate and bring the entireremaining image in coincidence with the reference image. Again, due tothe fact that the entire printing surface of the plate is readilyvisible, this registry operation becomes relatively simple.

As each subsequent printing plate is brought into registry with thereference image on the transparent sheet 111), it is clamped and thetension lockup pockets are milled into its under surface. Thus, it willbe appreciated that when the series of plates are locked into theprinting press, each plate of the color series going to make up acomplete color picture is in precise relative registry and thus capableof producing a true, effective color reproduction.

We claim as our invention:

1. The method of forming tension lockup pockets precisely located withrespect to the printing image in a curved stereotype printing platehaving a printing image, comprising the steps of supporting the plateentirely by its inner curved surface and thus exposing its entireprinting image, superimposing a transparent reference image which ispre-alined with respect to the pocket forming machine over said plateimage, shifting the plate both axially and peripherally to bring adesired portion of the plate image into precise alinement with thecorresponding portion of the reference image, distorting the platelongitudinally and circumferentially by applying nonalined forces tobring all other portions of the plate image into alinement with theremaining corresponding portions of said reference image, and forming aset of tension lockup pockets in the inner curved surface of the plate.

2. The method of alining on a forming machine each of a series of curvedstereotype color printing plates and forming tension lockup pocketstherein, comprising the steps of supporting a black key plate to exposeits entire printing image, laying a transparent flexible sheet over theblack key plate in fixed relation to the frame of the machine and takinga reference image on the underside of the sheet, clamping the platefirmly to the support, forming a set of tension lockup pockets in theinner surface of the black plate, removing the black plate andsupporting the first color plate of the series, and successively theremaining plates of the series, on the machine with the entire plateimage exposed, superimposing the transparent flexible sheet andreference image over said plate image, shifting the plate both axiallyand peripherally to bring a desired portion of the plate image in toprecise alinement with the corresponding portion of the reference image,distorting the plate longitudinally and circumferentially by applyingnon-alined forces to bring all of the portions of the plate image intoalinement with the remaining corresponding portions of said referenceimage, clamping the plate firmly to the support, forming a set oftension lockup pockets in the inner surface of the plate, and removingthe plate to replace it with the next plate of the series.

3. In a milling machine for preparing curved stereotype printing platesby automatically machining selected portions of the plates, a saddleassembly for supporting a plate during the machining operationcomprising, in combination, a semi-cylindrical saddle member having aplate receiving head end and a plate discharging rear end, an alinementstop positioned in a recess in the saddle member near said head end,said stop being retractable beneath the surface of said saddle memberand having a cam surface permitting plates sliding along said saddlemember from said head end to engage and cam said stop into said recess,resilient means to urge the alinement stop into its upraised position sothat it will snap into alining position when a plate has passedthereover, a distorting stop positioned in a recess near said rear endof the saddle, said distorting stop being retractable beneath thesurface of said saddle member, and means remote from said distortingstop operable to cause the stop to retract into its recess and allow aplate sliding on said saddle to pass thereover.

4. In a milling machine for preparing curved stereotype printing platesby automatically machining selected portions of the plates, a saddleassembly for supporting a plate during the machining operationcomprising, in combination, a semi-cylindrical saddle member having aplate receiving head end and a plate dscharging rear end, two alinementstops positioned in elongated recesses in the saddle member near saidhead end, said stops being retractable beneath the surface of saidsaddle member and each having a cam surface permitting plates slidingalong said saddle member from said head end to engage and cam said stopsinto their respective recesses, resilient means to urge the alinementstops into upraised positions so that they will snap into aliningposition when a plate has passed thereover, two distorting stopspositioned in elongated recesses near said rear end of the saddle, saiddistorting stops being retractable to a non-operable position beneaththe surface of said saddle member, means remote from said distortingstops operable to selectively cause the stops both to retract into theirrecesses to said non-operable position and allow a plate sliding on saidsaddle to pass thereover, and to move said stops while in raised, plateengaging position along their respective recesses, and means remote fromsaid positioning stops operable to selectively move the stops alongtheir respective recesses.

5. In a saddle assembly including a semi-cylindrical saddle foradjustably supporting a curved printing plate, a positionable stop forpositioning a plate on the saddle comprising, in combination, a pivotedfinger extending above the surface of said saddle and being resilientlyurged to its raised position, means for moving said finger forward andbackward along said surface so as to provide an adjustable abutment forpositioning a plate on the saddle surface, and a finger stop effectiveas an incident to the fingers backward travel, for pivoting the fingeragainst its resilient urging and thus for retracting it beneath saidsurface so that plates may freely slide thereover.

6. In a saddle assembly including a semi-cylindrical saddle foradjustably supporting a curved printing plate, a positionable stop forpositioning a plate on the saddle comprislng, in combination, a pivotedfinger extending above the surface of said saddle and being resilientlyurged to its raised position, screw means to move said finger forwardand backward along said surface and thus provide an adjustable abutmentfor positioning a plate on the saddle surface, and a finger retractingstop mounted near the end of the fingers backward movement to pivot thefinger against its resilient urging and thus retract it beneath saidsurface so that plates may freely slide thereover, said fingerretracting stop mounting being adjustable along the path of fingertravel so as to enable the point at which the finger rises above thesaddle surface to be varied in accordance with the size of plate beinghandled.

7. In a saddle assembly including a semi-cylindrical saddle foradjustably supporting a curved printing plate, a positionable stop forpositioning a plate on the saddle comprising, in combination, a pivotedfinger having a for ward face extending above the surface of said saddleand in stopping position being resiliently urged to its raised position,the forward face of said finger being reversely angled with respect tothe saddle surface, screw means to move said finger forward and backwardalong said surface and thus provide an adjustable abutment forpositioning a plate on the saddle surface, said angled forward fingerface being efiective to wedgingly hold down a plate against which it isurged, and a finger retracting stop effective near the end of thefingers backward travel to pivot the finger against its resilient urgingand thus retract it beneath said surface so that plates may freely slidethereover.

8. In a plate milling machine for milling tension lock up pockets in aset of color printing plates, the combination comprising a frame, asaddle mounted thereon, means including a pair of milling cuttersjournaled on said frame and extending through apertures provided in saidsaddle for milling pockets adjacent the respective straight edges of aplate, image transfer means in the form of a transparent sheet hingedlyanchored to said frame in a position to overlie plates successivelyintroduced onto said saddle, means for adjustably positioning the saidsaddle peripherally and axially relative to the frame, means includingstops mounted in the surface of said saddle for distorting a printingplate to provide precise register between an area of said plate and acorresponding image on said transparent sheet, and arcuate clamps onsaid frame for pressing a plate downwardly onto said saddle, said clampsbeing mounted for sliding movement endwise to an out of the way positionto enable access of said transparent sheet to all portions of successiveplates.

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